1. Field of the Invention
The present invention relates in general to automotive air conditioning systems and more particularly to automotive air conditioning systems of a type suitable for motor vehicles which exhibit an excellent fuel consumption, such as a motor vehicle which is constructed to stop its engine when stops due to a red light at a crossing or the like or a hybrid motor vehicle which is equipped with both an internal combustion engine and an electric motor and effectively powered by at least one of them. More specifically, the present invention relates to an air conditioning systems for such low fuel consumption motor vehicles, which is kept operative even when the motor vehicle is under an idling step stopping the engine.
2. Description of the Prior Art
In order to clarify the task of the present invention, a known automotive air conditioning system of the above-mentioned type will be described, which is disclosed in Japanese Laid-open Patent Application 10-236151.
The known automotive air conditioning system is constructed to keep operation of the compressor with an electric power even when the engine of an associated motor vehicle is stopped. For operation of the compressor, an electric motor powered by a battery mounted on the vehicle is practically used. The compressor is of a capacity variable type, and upon operation of the compressor by the electric motor, the capacity of the compressor is automatically lowered to lessen the load of the battery. With this, the capacity of not only the battery but also the electric motor can be reduced and the electric power supplied by the battery can be saved.
In the Laid-open Application, a measure is further disclosed wherein selection of one of the power sources (viz., the engine and the battery) is effected in accordance with the power actually needed by the cooling section of the air conditioning system. That is, when the needed power is higher than a predetermined level, the compressor is driven by the engine, while when the needed power is lower than the predetermined level, the compressor is driven by the electric motor. Particularly, the compressor has two operation modes, which are a high-power mode wherein the compressor is driven by the engine while keeping its normal higher capacity, and a low-power mode wherein the compressor is driven by the electric power while keeping its lower capacity.
In operation, upon stopping of the engine by a standstill of the vehicle due to, for example, a red light at a crossing, the compressor is shifted to the low-power mode and thus driven by the electric motor. When, thereafter, due to change of the light from red to blue, the engine of the vehicle is restarted, the compressor is shifted from the low-power mode to the high-power mode.
However, due to its inherent construction, the above-mentioned known automotive air conditioning system has failed to quickly carry out the shifting from the low-power mode to the high-power mode. In fact, several seconds are needed for carrying out the shifting, which include a time for stopping the electric motor, a time for returning the capacity of the compressor to the normal higher one and a time for restarting the engine. During this period, the compressor is kept inoperative and thus the cooling section of the air conditioning system can not exhibit its cooling performance effectively.
It is therefore an object of the present invention to provide an automotive air conditioning system which is free of the above-mentioned drawbacks.
According to a first aspect of the present invention, there is provided an air conditioning system for use in a motor vehicle powered by an internal combustion engine. The system comprises an electric motor powered by a battery; a compressor arranged to be powered by at least one of the internal combustion engine and the electric motor; and a control unit that controls the driving of the compressor, the control unit being configured to execute driving the compressor by only the electric motor when the combustion engine is under an idling stop; restarting the combustion engine upon expiration of a first given time from the time when the idling stop has occurred, so that thereafter the compressor is driven by both the combustion engine and the electric motor; and stopping the driving of the compressor by the electric motor upon expiration of a second given time from the restarting of the combustion engine, so that thereafter the compressor is driven by only the combustion engine.
According to a second aspect of the present invention, there is provided an air conditioning system for use in a motor vehicle powered by an internal combustion engine. The system comprises an electric motor powered by a battery; a capacity variable compressor arranged to be powered by at least one of the internal combustion engine and the electric motor; and a control unit that controls the driving of the compressor, the control unit being configured to execute (a) calculating a power needed for driving the compressor when the vehicle is ready for an idling stop of the engine; (b) starting the electric motor when it is decided that the calculated power is obtainable by only the electric motor, so that thereafter the compressor is driven by both the internal combustion engine and the electric motor; and (c) executing the idling stop upon expiration of a first predetermined time from the time when the electric motor has started.
According to a third aspect of the present invention, there is provided an air conditioning system for use in a motor vehicle powered by an internal combustion engine. The system comprises an electric motor powered by a battery; a capacity variable compressor arranged to be powered by at least one of the internal combustion engine and the electric motor, the compressor being controllable to have a high predetermined capacity, a lower level of a low predetermined capacity or a higher level of the low predetermined capacity; an air inlet opening controller arranged to inlet at least one of outside air and inside air into an air inlet opening of the air conditioning system, the air inlet opening controller having a first mode in which a normally conditioned air is led into a passenger room and a second mode in which the air inlet opening inlets either one of the outside air and inside air, that shows a temperature close to a target temperature of air blown into the passenger room; and a control unit that controls the driving of the compressor and the air inlet opening controller, the control unit being configured to execute (a) keeping the compressor to operate in the high predetermined capacity and keeping the air inlet opening controller to operate in the first mode when the compressor is driven by only the engine; (b) controlling the compressor to have the lower level of the low predetermined capacity and controlling the air inlet opening controller to assume the second mode upon receiving a signal representative of a previous notice of a temporary engine stop; (c) turning the electric motor ON; (d) stopping the engine upon passage of a given time from the turning ON of the electric motor; and (e) controlling the compressor to operate in the higher level of the low predetermined capacity upon passage of a given time from the engine stopping.